The present invention relates to a method for improving the recognition of a tire deflation in a tire pressure monitoring system in which at least one reference value (A) is generated on the basis of signals representing the wheel speeds of several vehicle wheels, in which case on the basis of the comparison of one currently determined reference value with at least one comparative value a pressure loss is inferred if the currently determined reference value exceeds respectively falls short of a predefined value. Furthermore, the invention relates to a computer program product defining an algorithm for the above method.
A reliable monitoring of the tire pressure on all wheels of a motor vehicle is very important for the safety of the motor vehicle. There are different approaches as to how tire pressure monitoring systems can be realized. There are so-called directly measuring tire pressure monitoring systems, as disclosed e.g. in the patent application DE 199 26 616 C2, detecting the respective pressure in the corresponding wheel by means of pressure sensors in the single wheels. Such systems monitor the tire pressure independently on all wheels. In addition, so-called indirectly measuring tire pressure monitoring systems are disclosed, e.g. in DE 100 58 140 A1 (DDS: Deflation Detection System), which are able to determine a pressure loss from auxiliary parameters, e.g. by comparing the information on the speed of the single wheels. Furthermore patent WO 2005/072995 A1 discloses a method of indirect tire pressure monitoring in which a known indirectly measuring tire pressure monitoring system (DDS) is improved taking into account the torsion natural frequency of the vehicle tires.
Indirectly measuring deflation detection methods on the basis of wheel speed information teach in so-called reference values serving essentially for crosswise comparison of the single wheels. In a four-wheel vehicle, for example, the consideration of three independent reference values has become an accepted standard. A first reference value describes the relation between two wheels on the same axle, a second reference value describes the relation between two wheels on the same vehicle side and a third reference value describes the relation between two wheels diagonally facing each other.
Furthermore, indirectly measuring tire pressure monitoring systems often use the information provided by systems already available in the motor vehicle, e.g. the wheel speed information of an anti-lock system (ABS), in order to draw conclusions regarding the tire pressures. This information has to be processed with statistical methods. In this case long processing time intervals may prevent the timely provision of the deflation detection system during the teach-in mode and/or when detecting pressure losses. Furthermore, the tire pressure monitoring systems are disabled if the quality of the input signals is insufficient, e.g. if the noise level of the signals is too high due to poor road conditions. In order to reduce teach-in and detection times and improve the availability of the system, it is necessary to adjust the system to the current road conditions.
Preferably, a method for indirectly detecting a pressure loss comprises a teach-in and a pressure monitoring phase. During the teach-in phase the comparative (reference) values are determined. During the pressure monitoring phase following the teach-in phase, currently determined reference values are compared with the values taught in, taking into account threshold values for the pressure loss detection.
It is the object of the invention to provide a method for adjusting a tire pressure monitoring system to the current road conditions which improves an indirectly measuring tire pressure monitoring system or a combined tire pressure monitoring system comprising an indirectly and a directly measuring tire pressure monitoring system.